1. Technical Field of the Invention
The present invention relates to a mobile telecommunications network and, in particular, to the selection of a default long distance carrier within a visited Public Land Mobile Network (PLMN).
2. Description of Related Art
With the development of Public Land Mobile Network (PLMN) telecommunications systems, mobile subscribers are able to freely travel within a particular country and utilize their mobile service. Even if the mobile subscriber is roaming within a visited PLMN, the home PLMN associated with the roaming mobile subscriber keeps track of the current location of the mobile subscriber and accordingly makes the necessary arrangements and communications to enable the mobile subscriber to receive and originate calls via another PLMN.
Whenever a particular mobile station travels into a visited PLMN, a mobile switching center (MSC) detecting the presence of the roaming mobile station performs a location update procedure with a home location register (HLR) associated with the roaming mobile station. By performing a location update, the serving MSC informs the HLR of the current location of the mobile station and also retrieves requisite subscriber data associated with the roaming mobile station from the HLR. The retrieved subscriber data are then stored within a visitor location register (VLR) attached to the serving MSC and subsequently utilized for providing mobile service to the roaming mobile station. Such retrieved data include the Mobile Subscriber Integrated Service Digital Network (MSISDN) number, feature application data, and Preferred Inter-Lata Carrier (PIC, or more commonly known as a long distance carrier) data. Utilizing the PIC data, even if the mobile station is roaming within a visited PLMN, if the long distance carrier specified by the received PIC data is providing service within the visited PLMN area, all long distance calls originated from or forwarded by the mobile stations are still routed through the specified long distance carrier. For example, if a particular mobile subscriber has designated American Telegraph & Telephone (AT&T) as his long distance carrier, even if the mobile subscriber is roaming outside of his home PLMN, and assuming AT&T is available, all long distance calls are still provided by AT&T within the visited PLMN.
However, in the event that PIC data are not provided to the visited MSC, or the long distance carrier specified by the retrieved PIC data does not provide long distance service within that visited PLMN area, conventionally, the visited MSC has no option but to choose one of the long distance carriers that does provide service within that particular PLMN area as a default provider. However, the arrangements made between the visited PLMN and the default long distance carrier might not always be the most favorable to the roaming mobile subscriber or his home PLMN.
Accordingly, there is a need for a mechanism to enable a home PLMN to specify a default long distance carrier to be utilized within a visited PLMN in case the long distance carrier selected by an associated mobile subscriber roaming within the visited PLMN is not available.